The combination of an approaching cold front and low pressure system produced high winds across portions of western and central Wyoming. Many locations had sustained winds over 50 mph with wind gusts over 70 mph.
Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS RIW wrote it up.
The combination of an approaching cold front and low pressure system produced high winds across portions of western and central Wyoming. Many locations had sustained winds over 50 mph with wind gusts over 70 mph. The maximum wind gust recorded was 79 mph at the Fales Rock RAWS site. Downslope wind gusts along the east slopes of the Wind River Range in and around Lander topped out between 60 and 75 mph during the early afternoon.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Riverton, WY wrote its last area forecast discussion before the first event at Dec 2, 2:54 AM MST, 6 hours 6 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 254 AM MST SUN DEC 2 2012 .SHORT TERM...TODAY THROUGH TUESDAY NIGHT AN ACTIVE WEATHER DAY IS EXPECTED ACROSS THE REGION AGAIN AS A POTENT SYSTEM APPROACHES FROM THE WEST. STRONG SOUTHWEST FLOW AHEAD OF THE SYSTEM WILL KEEP TEMPERATURES WARM...VERY WARM EAST OF THE DIVIDE WITH SOME HIGHS REACHING INTO THE 60S. THE SNOW LEVELS WILL AGAIN RISE UP ABOVE 8000 FEET TODAY AHEAD OF A STRONG COLD FRONT THAT WILL COME BLASTING THROUGH THIS EVENING...LOWERING THE SNOW LEVELS DOWN INTO THE VALLEYS AND DELIVERING A POWERFUL BURST OF SNOW TO THE WEST...IT WILL ALSO BRING A CHANCE OF RAIN AND SNOW EAST OF THE DIVIDE...EVENTUALLY TURNING TO ALL SNOW. SNOW WILL END ABRUPTLY AFTER MIDNIGHT TONIGHT AS THE UPPER TROUGH SWINGS INTO THE PLAINS AND HIGH PRESSURE BUILDS IN BEHIND IT ON MONDAY. THERE ARE A FEW WILD CARDS TODAY...FIRST...IT IS UNCERTAIN HOW FAR INTO THE LOWER ELEVATIONS THE HIGH WINDS WILL MOVE OFF OF THE ABSAROKAS AND THE WIND RIVER RANGE...WEST CODY...CLARK...MEETEETSE AND LANDER ARE AT THE GREATEST RISK OF RECEIVING DAMAGING WIND GUSTS THIS AFTERNOON AROUND FRONTAL PASSAGE...STRONG WINDS COULD ALSO LEAK THROUGH THE OWL CREEKS AND INTO THERMOPOLIS BUT THESE WINDS ARE NOT EXPECTED TO BE AS STRONG AS THE WINDS THAT COULD POTENTIALLY COME OFF OF THE WIND RIVERS AND ABSAROKAS. A PERIOD OF STRONG WIND AND HEAVY SNOW COULD ALSO MOVE THROUGH DUBOIS WITH FRONTAL PASSAGE...BUT IT THESE CONDITIONS ARE EXPECTED TO BE SHORT LIVED. ANOTHER AREA OF CONCERN WILL BE ACROSS THE SOUTH ALONG THE I80 CORRIDOR...THERE WILL BE WIDESPREAD CROSS WINDS THAT COULD HAVE HIGH IMPACT FOR TRAFFIC ALONG THE CORRIDOR BUT WINDS ARE NOT EXPECTED TO REACH WARNING CRITERIA...SO A SPECIAL WEATHER STATEMENT WAS ISSUED FOR THE CORRIDOR AS WELL AS FOR SOUTHERN LINCOLN COUNTY AND SUBLETTE COUNTY...WINDS WILL BE FAIRLY STRONG TODAY BUT ARE NOT EXPECTED TO REACH HIGH WIND CRITERIA. MONDAY WILL BE MUCH CALMER. HIGH PRESSURE BUILDS IN FROM THE WEST AS BENIGN WESTERLY FLOW SETS UP ACROSS THE REGION. THERE COULD BE A FEW LEFTOVER SHOWERS IN THE NORTHWEST AS SOME RESIDUAL MOISTURE WORKS WITH SOME WEAK ISENTROPIC LIFT. MONDAY WILL ALSO BE COOLER IN THE WAKE OF THE COLD FRONT...WITH TEMPERATURES MUCH CLOSER TO NORMAL FOR THIS TIME OF YEAR. TUESDAY WILL BRING ANOTHER ROUND OF SNOW TO THE WEST AS THE NEXT SYSTEM APPROACHES. SOUTHWEST FLOW AGAIN SETS UP AT THE SURFACE AS LEE SIDE TROUGHING DEVELOPS...PRODUCING MILD AND WINDY CONDITIONS EAST OF THE DIVIDE TUESDAY AFTERNOON. .LONG TERM...WEDNESDAY THROUGH SUNDAY THE LONG TERM WILL BEGIN WITH A MOIST WESTERLY FLOW...WITH THE POTENTIAL OF SIGNIFICANT SNOWFALL CONTINUING ACROSS THE WESTERN MOUNTAINS. TEMPERATURES WILL BE RELATIVELY WARM WITH A RAIN/SNOW OR MAINLY RAIN EVENT ACROSS THE WESTERN BASINS/VALLEYS. EAST OF THE DIVIDE...DOWNSLOPING WILL KEEP IT DRY AND CONTINUED UNSEASONABLY WARM. THE 00Z GFS HAS TRENDED TOWARD THE ECMWF SOLUTION WITH A WEAKER SYSTEM PUSHING EAST ALONG THE CANADIAN BORDER WEDNESDAY NIGHT/THURSDAY. THIS SYSTEM WOULD STILL BRING A COLD FRONT SOUTHWARD ACROSS THE AREA WEDNESDAY NIGHT/THURSDAY...AND GRADUALLY SHUT OFF THE MOIST WESTERLY FLOW INTO THE WESTERN MOUNTAINS. GLOBAL MODELS SHOW A LONGWAVE TROUGH GRADUALLY FORMING OVER THE CENTRAL CONUS LATE NEXT WEEK INTO NEXT WEEKEND...BUT DIFFER SUBSTANTIALLY ON THE DETAILS. THE 00Z GFS DIGS THIS TROUGH ACROSS THE ROCKIES SATURDAY/SUNDAY...WHILE THE ECMWF IS FARTHER EAST...AND BIT FASTER WITH THE INITIAL DIGGING OF THE TROUGH...AND MUCH MORE PROGRESSIVE WITH IT THROUGH TIME. THE GFS ENSEMBLES WERE A MIX BETWEEN THE OPERATIONAL GFS AND ECMWF SOLUTIONS. THUS HAVE BROAD BRUSH LOW POPS FOR LATE NEXT WEEK INTO NEXT WEEKEND WITH AN EMPHASIS ACROSS THE NORTHERN MOUNTAINS...AND HAVE GONE WITH A BLEND OF MODEL TEMPS UNTIL MODELS COME INTO BETTER AGREEMENT. ALTHOUGH IF THE OPERATIONAL GFS SOLUTION DOES COME TO FRUITION THE FORECAST AREA WOULD SEE MUCH COLDER TEMPS BY AROUND 10-15 DEGREES ACROSS THE NORTH SATURDAY...AND OVER THE ENTIRE AREA SUNDAY THAN CURRENTLY FORECAST. && .AVIATION.../12Z ISSUANCE/ EAST OF THE CONTINENTAL DIVIDE...VFR CONDITIONS WILL PREVAIL THROUGH 12Z MONDAY. THE EAST SLOPES OF THE WIND RIVER AND ABSAROKA MOUNTAINS WILL SEE SOME RAIN AND SNOW AFTER 19Z WITH MOUNTAIN OBSCURATION. THE BIGHORN MOUNTAINS WILL SEE SOME RAIN AND SNOW SHOWERS AROUND 06Z MONDAY THROUGH 12Z MONDAY. WINDY CONDITIONS WILL OCCUR OVER MANY LOCATIONS AFTER 19Z THROUGH 06Z MONDAY. AROUND THE CASPER AIRPORT THE WIND WILL BE QUITE STRONG TODAY INTO THIS EVENING. WEST OF THE CONTINENTAL DIVIDE...VFR CONDITIONS WILL PREVAIL THROUGH 18Z. SCATTERED RAIN AND SNOW SHOWERS WILL OCCUR IN THE WESTERN MOUNTAINS THROUGH 18Z. THEN ANOTHER PERIOD OF RAIN AND SNOW WILL MOVE INTO WESTERN WY AND CONTINUE THROUGH 06Z. MVFR TO IFR CONDITIONS WILL PREVAIL BY 22Z WITH FREQUENT MOUNTAIN OBSCURATION. WIND SPEEDS WILL ALSO BE INCREASING AFTER 18Z WITH GUSTY WIND OCCURRING THROUGH 06Z. A COLD FRONT WILL PUSH INTO WESTERN WY AROUND 01Z. THIS WILL PUSH EAST TO THE CONTINENTAL DIVIDE BY 06Z. RAIN WILL CHANGE TO SNOW BY 06Z OVER THE LOWER ELEVATIONS. CHECK THE LATEST TERMINAL FORECASTS FOR THIS AREA AS CONDITIONS MAY CHANGE QUITE RAPIDLY THIS AFTERNOON AND EVENING. && .FIRE WEATHER... A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA THIS EVENING...BRINGING A CHANCE OF RAIN AND SNOW TO THE ENTIRE AREA. HEAVIER SNOWFALL IS EXPECTED IN THE WESTERN MOUNTAINS WITH THE PRECIP IN THE FAR WEST VALLEYS BECOMING ALL SNOW BY TONIGHT...MUCH LIGHTER AMOUNTS ARE EXPECTED EAST OF THE DIVIDE. THIS SYSTEM WILL ALSO BRING WITH IT A LOT OF WIND WITH GUSTS OVER 80 MPH EXPECTED AT THE SUMMITS AND WIDESPREAD WINDY CONDITIONS EXPECTED IN THE LOWER ELEVATIONS AS WELL...WHERE GUSTS OVER 40 MPH WILL BE COMMON THROUGH THE DAY TODAY. MONDAY WILL BE MUCH COOLER AND CALMER WITH BASIN INVERSIONS FORMING ON MONDAY NIGHT WITH POOR SMOKE DISPERSAL. && .RIW WATCHES/WARNINGS/ADVISORIES... HIGH WIND WARNING FROM 8 AM THIS MORNING TO 3 AM MST MONDAY WYZ002-019-020. HIGH WIND WATCH FROM 2 PM MST THIS AFTERNOON THROUGH THIS EVENING WYZ018. WINTER STORM WARNING UNTIL 3 AM MST MONDAY WYZ001-012-024. WINTER WEATHER ADVISORY FROM 2 PM THIS AFTERNOON TO 3 AM MST MONDAY WYZ014-015. && SHORT TERM...ALLEN LONG TERM...WM AVIATION...AR FIRE WEATHER...ALLEN
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 300 AM MST SUN DEC 2 2012 WYZ001>020-022>030-031300- ABSAROKA MOUNTAINS-BIGHORN MOUNTAINS SOUTHEAST- BIGHORN MOUNTAINS WEST-CASPER MOUNTAIN-CODY FOOTHILLS- EAST SWEETWATER COUNTY-FLAMING GORGE- GREEN MOUNTAINS AND RATTLESNAKE RANGE-JACKSON HOLE-LANDER FOOTHILLS- NATRONA COUNTY LOWER ELEVATIONS-NORTH BIG HORN BASIN- NORTHEAST JOHNSON COUNTY-OWL CREEK AND BRIDGER MOUNTAINS- ROCK SPRINGS AND GREEN RIVER-SALT RIVER AND WYOMING RANGES- SOUTH LINCOLN COUNTY-SOUTHEAST BIG HORN BASIN- SOUTHEAST JOHNSON COUNTY-SOUTHWEST BIG HORN BASIN-STAR VALLEY- TETON AND GROS VENTRE MOUNTAINS-UPPER GREEN RIVER BASIN- UPPER GREEN RIVER BASIN FOOTHILLS-UPPER WIND RIVER BASIN- WIND RIVER BASIN-WIND RIVER MOUNTAINS EAST-WIND RIVER MOUNTAINS WEST- YELLOWSTONE NATIONAL PARK- 300 AM MST SUN DEC 2 2012 ...WINTER STORM BRINGING SIGNIFICANT SNOWFALL ACROSS WESTERN MOUNTAINS...AND VERY STRONG WINDS TO PORTIONS OF CENTRAL WYOMING TODAY AND TONIGHT... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT ANOTHER ROUND OF SIGNIFICANT SNOW...WILL OCCUR ACROSS THE WESTERN MOUNTAINS THIS AFTERNOON...AND EARLY TONIGHT. VERY STRONG WINDS... WILL ALSO OCCUR ACROSS PORTIONS OF CENTRAL WYOMING...ESPECIALLY ACROSS SOUTHEAST FREMONT AND NATRONA COUNTIES...AS WELL AS THE ABSAROKA MOUNTAINS. VERY STRONG WINDS COULD ALSO DEVELOP IN THE LANDER FOOTHILLS THIS EVENING. PLEASE SEE OTHER STATEMENTS FOR FURTHER DETAILS ABOUT THIS ONGOING STORM SYSTEM. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY TUESDAY AND WEDNESDAY...SIGNIFICANT SNOWFALL POSSIBLE ACROSS THE FAR WESTERN MOUNTAINS. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT SNOW AMOUNTS...AND WIND SPEEDS OVER 50 MPH. THANK YOU. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 529 AM MST SUN DEC 2 2012 WYZ013-023-025-022300- JACKSON HOLE-STAR VALLEY-UPPER GREEN RIVER BASIN FOOTHILLS- 529 AM MST SUN DEC 2 2012 PERIODS OF RAIN AND SNOW WILL CONTINUE TODAY AND TONIGHT. AREAS BELOW 7500 FEET WILL RECEIVE MAINLY RAIN AGAIN TODAY. SNOW LEVELS WILL SUDDENLY LOWER THIS EVENING...WITH THE PASSAGE OF A STRONG COLD FRONT. ONE TO THREE INCHES OF SNOW ARE POSSIBLE THIS EVENING ACROSS THE LOWER ELEVATIONS...WITH MUCH OF THE SNOW TAPERING OFF BY MIDNIGHT. MOUNTAIN PASSES WILL ONCE AGAIN BE SLICK AND TREACHEROUS TODAY AND TONIGHT. 21
The national radar mosaic for the moment the first event began.
4 high wind. Local standard time, as filed.
Many wind gusts past 58 mph were recorded at the Twenty Mile Hill sensor with a maximum gust of 63 mph. The Casper Airport ASOS reported a gust to 62 mph at 1153MST.
Numerous wind gusts over 60 mph were reported at the Fales Rock RAWS site. The maximum wind gust was 79 mph at 1410MST. A 59 mph gust was reported at the Camp Creek RAWS site as well.
Several wind gusts over 60 mph were reported at the North Fork of the Popo Agie station with a maximum gust of 75 mph. In addition, the Lander Airport ASOS recorded wind gusts of 60 and 58 mph.
The Wyoming Department of Transportation sensor at Chief Joseph reported sustained winds over 50 mph on the afternoon and evening of December 2. Wind gusts as high as 74 mph were reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2012Every state in 2012This day in weather historyWarnings in Wyoming, December 2012
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 416260, 416259, 416258, 416256.